Surface Engineering of Thermoplastic Materials and Tooling

ABSTRACT

A prepared mold tool having a thermoplastic surface layer polymer coating on the mold surface of the mold tool or prepared prepreg having a thermoplastic surface layer polymer coating on the surface of the thermoplastic fiber reinforced prepreg are described that enhance first ply laydown of thermoplastic fiber reinforced composite prepregs onto mold tools for prepreg forming or in situ tape placement. Resulting thermoplastic fiber reinforced composite parts from a thermoplastic fiber reinforced thermoplastic composite material having structural reinforcement fibers with one or more high performance polymers, and a thermoplastic surface layer polymer coating which forms a polymer blend with the high performance polymers of the thermoplastic fiber reinforced composite material thereby imparting improved properties, and methods for making and using same, are provided herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter of the present invention relates to fiber reinforcedthermoplastic plastic composite materials and particularly to applying asurface layer polymer coating to a composite forming mold tool or to afiber reinforced thermoplastic prepreg composite material to enhance thefirst ply laydown of the prepreg onto the composite forming mold toolfor prepreg forming or in situ automated laydown tape placement. In situapplication of the surface layer polymer coating during or beforeautomated laydown may also provide a beneficial resin rich interlaminarlayer between each layer of fiber reinforced thermoplastic compositematerial. The surface layer polymer coating is preferably thermoplasticparticles applied by plasma spraying to the mold tool or prepreg to forma substantially fused layer of thermoplastic particles. Moreparticularly, in certain embodiments the present invention relates tolayered fiber reinforced thermoplastic prepreg for use in rapidlamination and forming processes where such fiber reinforcedthermoplastic prepreg are useful in aerospace and other high-performanceautomotive/industrial applications.

2. Description of the Related Art

Reinforced thermoplastic and thermoset materials have wide applicationin, for example, the aerospace, automotive, industrial/chemical, andsporting goods industries. Thermosetting resins are impregnated into thefiber reinforcing material before curing, while the resinous materialsare low in viscosity. Thermoset composites suffer from disadvantagesincluding processing problems concerned with removing entrained air orvolatiles so that a void-free matrix is produced. Thermoset compositesmade by the prepreg method require lengthy cure times with alternatingpressures to control the flow of the resin as it cures to preventbubbles in the matrix. While traditional fabrication of structuresutilized hand placement of thermosetting prepreg plies onto a tool,current fabrication of large structures utilize robotic placement of thethermoset composite material onto the tool to increase production rate.The overall production rate for a structural component is limited by thelengthy cure in the autoclave process step and related operations toprepare the material for that process step. Some high volume processes,such as resin infusion avoid the prepreg step but still require specialequipment and materials along with constant monitoring of the processover the length of the cure time (e.g., U.S. Pat. Nos. 4,132,755, and5,721,034).

Thermoplastic resin compositions are more difficult to impregnate intothe fiber reinforcing material because of their comparatively higherviscosity than thermosetting resin compositions. On the other hand,thermoplastic resin compositions offer a number of benefits overthermosetting resin compositions. For example, thermoplastic prepregscan be more rapidly fabricated into articles and fabrication with fiberreinforced thermoplastic composite materials may utilize roboticautomated laydown tape placement of the fiber reinforced thermoplasticcomposite material onto a mold tool to increase production rate. Thismay be through a multiple-step robotic arm that pre-heats the priorlayer of fiber reinforced thermoplastic composite material beforeheating and laying the subsequent layer of fiber reinforcedthermoplastic composite material on top of it.

Thermoplastic resins are long chain polymers of high molecular weightthat are highly viscous when melted and are often non-Newtonian in theirflow behavior. Thus, whereas thermosets have viscosities in the range of100 to 5,000 centipoise (0.1 to 5 Pa*s), thermoplastics have meltviscosities ranging from 5,000 to 20,000,000 centipoise (5 to 20,000Pa*s), and more typically from 20,000 to 1,000,000 centipoise (20 to1000 Pa*s). Despite a viscosity difference of three orders of magnitudebetween thermosets and thermoplastics, some processes have been appliedto both types of matrices for laminating fibrous materials.

Fiber reinforced plastic materials may be manufactured by firstimpregnating the fiber reinforcement with resin to form a prepreg, thenconsolidating two or more prepregs into a laminate, optionally withadditional forming steps. A few processes apply melt directly to thefibers. A tape can be made by coating a dry web of collimated fiberswith the polymer and applying a heated process that forces the polymerinto and around the fibers (e.g., see U.S. Pat. Nos. 4,549,920 and4,559,262). Another process used to coat and impregnate a dry web ofcollimated fibers is by pulling the web through an aqueous slurry offine thermoplastic polymer particles whereby the polymer particles aretrapped within the filament bundles. Subsequent heat and pressure in theprocess boils off the water and then melts the polymer to force it intoand around the filament bundles. This process is described in U.S. Pat.Nos. 6,372,294, 5,725,710, 4,883,552 and 4,792,481. A modification tothe aqueous slurry impregnation process is to eliminate the use of waterand surfactant as dispersing agents for the polymer particles andinstead electrostatically charge the particles in a fluidized bed of airto trap the particles in the filament bundle. Subsequent zones of heatand pressure melt the polymer to coat/impregnate the filament bundle asgiven in U.S. Pat. No. 5,094,883. Thus, for those skilled in the art,there are multiple methods to coat and/or impregnate a fibrous substrategiven the available process equipment, and proper selection of polymerproduct form (flake, fine powder, film, non-woven veil, pellets) andmelt viscosity.

Both thermoplastic and thermoset composites can be formed into thinflexible sheets or strips, referred to as tape. This allows compositecomponents to be formed by laying down the composite tape in a moldingtool, with the thickness of the component being locally varied accordingto the number of layers of composite tape laid down and also thedirection of one or more layers of the tape being controllable so as tocontrol the final structural properties of the formed compositecomponent. The laid up components are then “consolidated”, a processwhich cases involves heating the composite structure so that thethermoset or thermoplastic matrix softens to a sufficient degree to forma single unified matrix, and applying sufficient pressure to thesoftened matrix to expel any trapped air from the matrix.

In terms of final structural properties, thermoplastic composites havesuperior impact and damage resistance properties to those of thermosetcomposites and are generally tougher and more resistant to chemicalattack, all of which are preferable properties within aerospaceapplications. Furthermore, since thermoplastic composites may berepeatedly reheated and remolded, they are inherently recyclable, whichis an increasingly important consideration.

However, thermoset composite tape has one property that, in relation tothe laying up process, currently makes it the material of choice for usein aerospace composite components. This property is that the thermosettape is inherently sticky, or is said to have tack. This tackinessallows the thermoset tape to adhere to both the complex shaped moldsurfaces often required for composite components within the aerospaceindustry, and also for separate layers of the thermoset tape to adhereto one another once the initial layer has been applied to the moldsurface, thus making the laying up process relatively easy andconvenient to physically manage.

In contrast, thermoplastic composite tape has no tackiness.Consequently, it is problematic to make the thermoplastic composite tapeadhere to complex mold surfaces during the lay-up process. Existinglay-up techniques combine local consolidation and melting of thethermoplastic composite material to enable the initial, base layer to bebuilt up only as long as the base layer is firmly held to the surface ofthe mold tool. Previously proposed solutions to this problem haveincluded applying a separate double-sided adhesive tape as an initiallayer to the mold surface to which the first layer of thermoplasticcomposite tape subsequently adheres. Similarly, it has also beenproposed to spray an adhesive to the surface of the mold. Whilst bothproposed solutions allow the first layer of thermoplastic composite tapeto be successfully applied to complex shaped mold surfaces, theyintroduce their own problem of how to subsequently remove the formedcomposite component from the mold when the laying up process iscomplete, since the component is now effectively bonded to the moldsurface. Consequently, it is still presently preferred to use thermosetcomposite materials despite the superior physical properties provided bythermoplastic composite materials.

Known methods for fabrication of composite articles include manual andautomated fabrication. Manual fabrication entails manual cutting andplacement of material by a technician to a surface of the mandrel. Thismethod of fabrication is time consuming and cost intensive, and canpossibly result in non-uniformity in the lay-up.

Automated fabrication techniques include flat tape laminating machines(FTLM) and contour tape laminating machines (CTLM). Typically, both FTLMand CTLM employ a solitary composite material dispenser that travelsover the work surface onto which the composite material is to beapplied. The composite material is typically laid down a single row (ofcomposite material) at a time to create a layer of a desired width andlength. Additional layers may thereafter be built up onto a prior layerto provide the lay-up with a desired thickness. FTLM's typically applycomposite material to a flat transfer sheet; the transfer sheet andlay-up are subsequently removed from the FTLM and placed onto a tool,mold or mandrel. In contrast, CTLM's typically apply composite materialdirectly to the work surface of a tool, mold or mandrel. FLTM and CTLMmachines are also known as automated tape laydown (ATL) and automatedfiber placement (AFP) machines, with the dispenser commonly referred toas a tape head.

The productivity of ATL/AFP machines is dependent on machine parameters,composite part lay-up features, and material characteristics. Machineparameters such as start/stop time, course transition time, andcut/adding plies determine the total time the tape head on the ATL/AFPis laying material on the mandrel. Composite lay-up features such aslocalized ply build-ups and part dimensions also influence the totalproductivity of the ATL/AFP machines.

The ideal process for creating thermoplastic parts is in situfabrication wherein a part is created by robotically placing andconsolidating thermoplastic materials onto the molding tool in one step.Thermoplastic composite materials lack tack, which complicates the useof hand and automated lay-up operations, especially of the first plyagainst the molding tool surface.

Key material factors that influence ATL/AFP machine productivity aresimilar for a thermoset resin matrix composite when compared with athermoplastic matrix composite yet there are a couple of keydifferences. For thermoset resin matrix composites, key factors areimpregnation levels, surface resin coverage, and “tack”. Tack is theadhesion level necessary to maintain the position of the tape/tow on thetool or lay-up after it has been deposited on it. Due to the unreactednature of the thermoset resin, the ATL/AFP process is generallyperformed at room temperature but in humidity controlled rooms due tothe moisture sensitivity on the tack level of the material. Among otherimpacts, tack affects the ability to lay down the first ply of materialonto the tool. First ply lay-down of thermoplastic materials iscomplicated by the lack of tack to hold the first layer down to thetool.

The first composite ply to be placed against any tool requires someadhesive or other force to position the material and hold it againstgravity or the stiffness of the material. When thermoset materials areused, the polymer that is above the T_(g) at the lay-down head willprovide this force. When the matrix resin is a high performancethermoplastic, this T_(g) temperature is substantially higher andsubstantially above room temperature. Heating the mold tool, providing avacuum source, use of a lower temperature film or using a solvatedthermoplastic polymer to provide the restraining force are all methodscurrently used. Each of these methods has limitations in cost, toolcomplexity, variation to the dimensions of the part or requireshazardous solvents to practice.

A method known to overcome the limitation of low tack in thermoplasticsmanufacturing is to provide a mold tool made of a porous material andapply a negative pressure to the porous material so as to create anegative pressure at the mold surface, whereby the thermoplasticcomposite material is held against the mold surface by virtue of thenegative pressure at the mold surface when the initial layer ofthermoplastic composite material is laid onto the mold surface. Thethermoplastic material could thereafter be consolidated and heated toform the thermoplastic composite material (see, e.g., U.S. PatentApplication Publication No. 2011/0005666).

Thermoplastic matrix composites have similar key factors as thermosetmatrix composites for ATL/AFP machine productivity, but thethermoplastics polymer tape lack tack at ambient conditions.Thermoplastics generally have low surface energies, a high glasstransition temperature (“T_(g)”), making adhesion at room temperatureunlikely. Furthermore, the high performance thermoplastic matrices arein their glass state at room temperature making the molecular diffusionmechanism for tack virtually impossible. Thus, tack is achieved inthermoplastic composites by dynamically applying additional energy inthe form of thermal, ultrasonic, optical (laser), and/or electromagnetic(induction) to the lay-up and incoming tape to raise the temperature ofthe materials above their softening and/or melt temperature in order tofacilitate molecular diffusion of the polymer chains to occur betweenthe two surfaces. Once the polymer chains have diffused across thesurface, the additional energy added to the materials needs to beremoved to a level that will prevent distortion of the laminated lay-uponce the lamination pressure from the ATL/AFP head is removed. Thisrapid flux of energy into and out of the lay-up makes it desirable froman energy usage and lay down speed to perform this process step at thelowest possible temperature and energy without compromising on thetemperature performance of the resulting composite part.

Consolidation is typically necessary to remove voids that result fromthe inability of the resin to fully displace air from the fiber bundle,tow, or roving during the processes that have been used to impregnatethe fibers with resin. The individually impregnated roving yarns, tows,plies, or layers of prepregs are usually consolidated by heat andpressure by compacting in an autoclave. The consolidation step hasgenerally required the application of very high pressures and hightemperatures under vacuum for relatively long times. Furthermore, theconsolidation process step using an autoclave or oven requires a“bagging” operation to provide the lay-up with a sealed membrane overthe tool to allow a vacuum to be applied for removal of air and toprovide the pressure differential necessary to effect consolidation inthe autoclave. This process step further reduces the total productivityof the composite part operation. Thus, for a thermoplastic composite itwould be advantageous to in-situ consolidate to a low void compositewhile laminating the tape to the substrate with the ATL/AFP machine.This process is typically referred to as in situ ATL/AFP and thematerial used in that process called an in situ grade tape.

In general, thermoplastic composites have had limited success to date,due to a variety of factors including high processing temperatures(currently around 400° C.), high pressures, and prolonged molding timesneeded to produce good quality laminates. Most of the efforts have beenfocused on combining high performance polymers to structural fiberswhich has only exacerbated the process problems. Because the length oftime typically required to properly consolidate the prepreg pliesdetermines the production rate for the part, it would be desirable toachieve the best consolidation in the shortest amount of time. Moreover,lower consolidation pressures or temperatures and shorter consolidationtimes will result in a less expensive production process due to loweredconsumption of energy per piece for molding and other manufacturingbenefits.

Accordingly, the fiber-reinforced thermoplastic materials and methodspresently available for producing light-weight, toughened compositesrequire further improvement. Thermoplastic materials having improvedprocess speeds on automated lay-up machines and lower processingtemperatures and having no autoclave or oven step would be a usefuladvance in the art and could find rapid acceptance in the aerospace andhigh-performance automotive industries, among others.

SUMMARY OF THE INVENTION

The present invention provides a prepared mold tool having a releasablyadhered surface layer polymer coating on the mold surface of the moldtool. The mold tool is a non-porous metal mold tool having a moldsurface with a texture and a release film adhered to the textured moldsurface of the mold tool and the surface layer polymer coating adheredto the release film. The surface layer polymer coating is preferably aplurality of thermoplastic particles applied to the mold surface byplasma spray creating a substantially fused layer of thermoplasticparticles. The prepared mold tool aids placement and adhesion of thefirst ply of a fiber reinforced thermoplastic composite material such asa thermoplastic prepreg, a thermoplastic unidirectional tape or web,fiber tow/preg, or fabric, or non-woven materials such as a mat or veil.Thermoplastic prepregs are traditionally applied by hand lay-down whilethermoplastic unidirectional tapes are applied by in situ automatedlaydown tape placement against a mold tool.

The present invention also involves a method for preparing a preparedmold tool for first ply laydown by providing a solid metal, non-porousmold tool having a mold surface, applying a texture to a mold surface ofthe mold tool, applying a release film to the mold surface having atexture and finally applying a surface layer polymer coating by plasmaspraying thermoplastic particles onto the release film on the moldsurface of the mold tool having the texture.

A further embodiment of the present invention provides a preparedprepreg having fiber reinforced thermoplastic composite material with asurface layer polymer coating adhered to one or both surfaces of thecomposite material. The surface layer polymer coating is preferably aplurality of thermoplastic particles applied to the surface of the fiberreinforced thermoplastic composite materials by plasma spray to create asubstantially fused layer of thermoplastic particles on the surface. Theprepared prepreg aids placement of the first ply of fiber reinforcedthermoplastic composite material to a mold surface of a mold tool andmay further improve resulting composite part interlaminar propertiesbetween plies of composite material.

The present invention also involves a method for preparing the preparedprepreg by providing a fiber reinforced thermoplastic composite materialsuch as a thermoplastic prepreg or a thermoplastic unidirectional tapeand then applying a surface layer polymer coating by plasma sprayingthermoplastic particles onto one or both of the surfaces of the fiberreinforced thermoplastic composite material.

In the present invention, the surface layer polymer coating provides acompatible chemistry placed against the mold tool which maintains thedimensions, lowers the temperature requirement for adhesion, and allowsthe use of hybrid polymer and optional inclusion of conductive coatingsfor lightning strike in the surface layer polymer coating. Thiscompatible chemistry of the present invention improves adhesion of thefirst ply of fiber reinforced thermoplastic composite material to themold surface of the mold tool while maintaining ease of separation ofthe resulting composite part from the mold tool. When the resultingcomposite part is removed from the mold tool, the surface layer polymercoating will transfer to the resulting composite part as a surface skinthat may impart desirable characteristics to the resulting compositepart. Such desirable characteristics such as fire, corrosion or wearprotection may come from multi-functional additives to the surface layerpolymer coating.

Of particular importance is where the surface layer polymer coating is ahigh performance thermoplastic such as poly(ether ether ketone) (“PEEK”)or poly(ether ketone ketone) (“PEKK”).

The present invention seeks to improve first-ply lay-down by reducingcomposite part failure due to material de-bonding against the mold toolduring processing, as well as improving chemical compatibility in thehigh performance thermoplastic polymer. Concepts including fastcrystallization or amorphous materials as well as discrete metalliclayers and ground fiber mixtures are possible. Furthermore, thisdiscovery also reduces the initial capital and facility cost investmentto produce large composites.

The present invention also provides methods for manufacturing aresulting thermoplastic composite part with a thickness in the range of25 to 400 microns that has improved processing times on ATL machines andmanufacturing equipment.

Accordingly, the invention described in detail herein provides, in oneaspect, a prepared mold tool having a surface layer polymer coating ofat least one high performance polymer, and a prepared prepreg havingsurface layer polymer coating on one or both surfaces.

In another aspect, the invention relates to articles of manufacture madefrom the thermoplastic composites according to the invention describedherein. Such articles are useful, for example, in the aircraft/aerospaceindustries among others.

In situ grade thermoplastic composite material tapes for use on anautomated tape laydown or automated fiber placement machine are alsoprovided.

These and other features and advantages of this invention will becomeapparent from the following detailed description of the various aspectsof the invention taken in conjunction with the accompanying Figures andExamples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a side plan view of one embodiment of the present inventionillustrating the configuration of the prepared tool (10) including thenon-porous metal mold tool (20), the textured mold surface (30) of themold tool, the release film (40) and the surface layer polymer coating(50).

FIG. 1 b is a perspective view of the embodiment of FIG. 1 aillustrating the configuration of the prepared tool (10) including thenon-porous metal mold tool (20), the textured mold surface (30) of themold tool, a sealer and the applied release film (40) and the surfacelayer polymer coating (50) shown as substantially fused thermoplasticparticles after application by plasma spraying.

FIG. 2 a illustrates a perspective view of in situ application of thesurface layer polymer coating (50) from a plasma spray head (70) onto anon-porous metal tool (20) followed by application of a first plythermoplastic fiber reinforced composite material (60) and compacted byan AFP/ATL laydown roller (80).

FIG. 2 b further illustrates a perspective view of in situ applicationof the thermoplastic interlaminar layer (90) (e.g., thermoplasticparticles) from a plasma spray head (70) onto a previously appliedthermoplastic composite tape material (60) followed by application of asubsequent ply thermoplastic fiber reinforced composite material (60)and compacted by an ATL laydown roller (80) providing in situ appliedthermoplastic interlaminar layer (90) between layers of thermoplasticfiber reinforced composite material during automated tape lay-down.

FIG. 3 illustrates a side plan view of a surface layer polymer coatingapplied to a thermoplastic composite prepreg by plasma spraying athermoplastic polymer coating (50) from a plasma spray head (70) ontoone or both surfaces of a composite material (60) to form a plasmacoated thermoplastic composite material (100).

FIG. 4 a illustrates the mean spacing of local peaks of profile of ahigh temperature mold tool and a thermoplastic surface layer polymercoating using a profilometer.

FIG. 4 b illustrates the spacing of peaks in the y-axis.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a prepared mold tool having a surfacelayer polymer coating applied to the release side mold surface of themold tool to enhance adhesion of the first ply of thermoplastic fiberreinforced composite material to the mold surface.

FIG. 1 a illustrates such an embodiment of the present inventionproviding the configuration of a prepared tool (10), including thenon-porous metal mold tool (20) with a textured molding surface (30), arelease film (40) and a surface layer polymer coating (50) releasablyapplied to the release film. FIG. 1 b illustrates such an embodiment ofthe present invention providing the prepared tool (10) detailing thesurface layer polymer coating (50) shown as substantially fusedthermoplastic particles applied by plasma spraying.

Importantly, surface layer polymer coating (50) may be applied to therelease side mold surface of mold tool (20) through use of plasma sprayduring in situ automated tape laydown. Continued plasma spray of thesurface layer polymer during automated tape laydown on top of a priorply of fiber reinforced composite material (60) provides a thermoplasticinterlaminar layer (90) that can impart beneficial properties such astoughening to the resulting composite part.

FIG. 2 a illustrates in situ application of the surface layer polymercoating (50) such as thermoplastic particles from a plasma spray head(70) onto a non-porous metal mold tool (20) and then the application ofthermoplastic fiber reinforced composite material (60) and compacted byan ATL laydown roller (80).

FIG. 2 b further illustrates continued plasma spray of the surface layerpolymer by plasma spray head (70) during automated tape laydown therebyproviding a thermoplastic interlaminar layer (90), and then applicationof a subsequent ply of thermoplastic fiber reinforced composite material(60) compacted by ATL laydown roller (80). Continued application of thesurface layer polymer coating such as a thermoplastic from a plasmaspray head (70) onto a previously ply of thermoplastic fiber reinforcedcomposite material (60) and then a subsequent ply of thermoplasticcomposite material (60) applied and compacted by an ATL laydown roller(80) provides an in situ applied interlaminar thermoplastic layer (90)between the layers of thermoplastic fiber reinforced composite materialand subsequently applied thermoplastic fiber reinforced compositematerial during automated tape lay-down.

Thermoplastic interlaminar layer (90) and surface layer polymer coating(50) are each high performance thermoplastic polymers, and may be thesame or different materials and may contain the same or differentmultifunctional additives. This versatility in selection of theparticular high performance thermoplastic polymer permits selection ofthe optimal materials for the surface layer coating (50) and theinterlaminar layer (90).

Similarly, the first ply fiber reinforced composite material (60) andthe subsequent plies of fiber reinforced composite material (60) areeach compatible material, but may be the same or different compositionsdepending upon the properties desired for each layer.

Alternatively, the present invention provides prepared prepreg having asurface layer polymer coating applied directly to one or more surfacesof a thermoplastic fiber reinforced composite prepreg material toenhance adhesion of the first ply of the thermoplastic fiber reinforcedcomposite material to the mold surface of the mold tool and to furtherprovide a beneficial interlaminar layer to the resulting composite part.

FIG. 3 illustrates a prepreg (100) prepared by applying a surface layerpolymer coating (50) to both surfaces of a thermoplastic fiberreinforced composite material (60) by plasma spraying thermoplasticparticles from a plasma spray head (70) onto the surfaces of a fiberreinforced composite material (60), thereby forming the prepared prepreg(100). Depending upon the performance of the resulting composite partsought, the surface layer polymer coating may be the same or differenton each side of the prepared prepreg (100).

Prepared tool (10) of the present invention incorporates a surface layerpolymer coating (50) that is releasably adhered to the mold surface of amold tool (20). Preferably, a release film (40) is interposed betweenthe mold surface of the mold tool (20) and the surface layer polymercoating (50). Additionally, for optimal control of adhesion of thesurface layer polymer coating (50) to the mold surface, the mold surfaceof the mold tool (20) is a textured surface (30). Prepared tool (10) maybe utilized for laydown of fiber reinforced composite material by handor by ATL as may be desired. Prepared tool (10) provides optimalcontrolled adhesion of the first ply fiber reinforced composite materialduring either hand or ATL application.

FIG. 2 a illustrates laydown of a first ply fiber reinforced compositematerial (60) by automated tape laydown placement onto the mold surfaceof mold tool (20). When using a tape prepreg as the fiber reinforcedcomposite material (60), a plasma spray head (70) will spraythermoplastic particles onto the mold surface, forming the surface layerpolymer coating (50) on the mold surface for preparation of the moldsurface of mold tool (20). Subsequently, an ATL laydown roller (80) laysdown and releasably adheres the tape prepreg fiber reinforced compositematerial (60) onto the surface layer polymer coating (50) on the moldsurface of the mold tool (20). Continued application of this process isillustrated by FIG. 2 b wherein subsequent layers of fiber reinforcedcomposite material (60) are applied by spraying thermoplastic particlesonto the surface of a previously adhered layer of fiber reinforcedcomposite material (60) using a plasma spray head (70), and thenapplying with the ATL laydown roller (80) a subsequent ply of fiberreinforced composite material to create a thermoplastic interlaminarlayer (90). This thermoplastic interlaminar layer (90) can providebeneficial toughening or other multifunctional benefits as desired.

Prepreg (100) of the present invention is prepared by applying a surfacelayer polymer coating (50) to one or both surfaces of a fiber reinforcedcomposite material (60) directly before or during in situ laydown of thefiber reinforced composite material (60). A flow of fiber reinforcedcomposite material (60) is passed between one or more plasma spray heads(70) that apply surface layer polymer coating (50) to one or both sidesof the composite material (60), thereby forming the prepared prepreg(100). This prepared prepreg (100) can then be directly applied to amold tool or a prepared tool (10) by hand laydown or by ATL as desired,and is releasably adhered to the mold surface of the mold tool orprepared tool (10). Prepared prepreg (100) can be applied as a tapeprepreg by an ATL laydown roller as shown in FIG. 2 a, without the needfor a separate plasma spray head (70) for applying a first ply of fiberreinforced composite material having a surface layer polymer coating(50) adjacent to the mold surface of the mold tool (20). The moldsurface is preferably a textured mold surface (30). Prepared prepreg(100) can save manufacturing costs and create more uniform manufacturingconditions while providing the same potential multifunctional benefits.If the surface layer polymer coating (50) is applied to both surfaces ofa fiber reinforced composite material (60), the coating (50) on eachsurface can have the same or different compositions.

Various methods of applying surface layer polymer coating (50) areavailable and known in the art, such as by spraying a solvent basedpolymer solution onto the mold surface of a metal mold tool, by handapplying a water based slurry, by a plasma spray application, or anelectrostatic powder coating and fusing method, among others.

One particularly preferred embodiment of the present invention providesfor plasma spray application of the surface layer polymer onto the moldsurface of a mold tool (20) forming a prepared tool (10) as illustratedin FIGS. 1 a and 1 b, or directly onto the fiber reinforced compositematerial (60) as depicted in FIG. 3 to form prepared prepreg (100). Whenthe surface layer polymer coating (50) is applied using a plasma spraygun, the surface layer polymer is introduced to the plasma gun in theform of solid particles, preferably thermoplastic particles with a D₉₀diameter (wherein ninety percent of the particles are smaller than thenumber, by volume) from 90 to 180 μm and more preferably from 150 to 185μm. The particles are applied using a low velocity, high temperatureplasma.

A preferred high performance polymer surface layer polymer particle isPEEK polymer.

Surface layer polymer coating (50) is substantially continuous, but maybe discontinuous at lower thickness levels along the mold surface,especially depending upon the level of roughness of textured surface(30) to which it is applied. It is desired to be continuous over atleast 50% of the mold surface, and more preferably at least 90% of themold surface and optimally, at least 98% of the mold surface. Whenutilizing a plasma spray head (70) to apply the surface layer polymercoating (50), the heated thermoplastic particles impact and adhere tothe mold surface as molten particles and the resulting surface layercoating (50) can appear as a discontinuous plurality of beads that arewell fused thermoplastic particles, but not all are melt fused together,forming the partially discontinuous film.

The high performance polymer particle size is D₉₀ of about 100 μm toabout 400 μm. Preferably, the polymer particle sizes is in the D₉₀ rangeof from about 125 μm to about 250 μm, and most preferably from about 150to about 200 μm for optimum plasma spray application results. Whenapplied, the high performance polymer particles are exposed to a plasmaspray head temperature in the range of about 1800° F. to about 2000° F.at a velocity of about 350 to about 400 μm/second at the vent portnozzle section of the plasma spray applicator.

Useful commercially available plasma spray applicator include thePraxair SG 10 plasma spray applicator or a Sulzer Metco plasma sprayapplicator. The high performance polymer is introduced into the plasmaspray head as a solid particle. The plasma spray applicator then directsthe solid particles into the plasma jet stream to heat and acceleratethe particles to a high velocity.

For best performance, the mold tool (20) is pre-heated to about 250° F.(121° C.) to aid in adhering the surface layer polymer coating (50) tothe mold surface of the mold tool (20).

For preparation of a prepared mold tool, plasma spraying should applysurface layer polymer coating (50) to the mold surface of the mold tool(20) at a thickness in the range from 0.001 to 0.010 inch thick layer.In some embodiments, the thickness of the surface layer polymer coating(50) is more preferably about 0.002 inches. This thickness is intendedto aid in adhesion of the first ply without adding significant weight tothe resulting composite part.

In preparing a prepared prepreg (100), plasma spraying should apply asurface layer polymer coating (50) onto a fiber reinforced thermoplasticcomposite material (60) at a thickness of from about 0.0005 to about0.010 inches per layer. In some embodiments, the thickness of thesurface layer polymer can be from about 0.001 to about 0.008 inches perlayer.

Surface layer polymer coating (50) can be releasably applied to the moldsurface of mold tool (20) to allow effective release of the resultingcomposite part from the mold surface of the mold tool. While adifficulty with automated tape lay-down of thermoplastic fiberreinforced composite materials is ineffective adhesion of the first plyto the mold surface of the mold tool, the thermoplastic surface layerpolymer coating should not adhere so strongly to the mold surface of themold tool so that when removal is attempted, the thermoplastic surfacelayer polymer coating is compromised and the resulting thermoplasticcomposite part is damaged. This is especially important when thethermoplastic surface layer polymer coating contains anymulti-functional agent such as described herein to further enhance thesurface properties of the resulting thermoplastic composite part.

For purposes of this invention, the thermoplastic surface layer polymercoating is said to be releasably applied when the resultingthermoplastic composite part made on a mold tool with a thermoplasticsurface layer polymer coating releases from the mold tool with slight tomodest pressure, while the surface layer polymer coating does not detachduring the automated in situ laydown of the thermoplastic fiberreinforced composite material.

The thermoplastic surface layer polymer (50) on the mold surface of moldtool (20) can improve the surface quality and properties of theresulting thermoplastic composite part once it is removed from the moldtool due to the qualities of the resin rich thermoplastic surface layerpolymer coating, the enhanced surface texture, and optionalmulti-functional additives which can be incorporated therein.

The surface layer polymer coating (50) can comprise a high performancepolymer chosen from a slow crystallizing, semi-crystalline polymer or anamorphous polymer (or mixtures thereof), such that the thermoplasticsurface layer polymer coating (50) forms a miscible and/or compatibleblend with the high performance thermoplastic polymer of the fiberreinforced thermoplastic composite material (60). The surface layerpolymer coating (50) can be any one of the high performancethermoplastic polymers described herein that is applied to the moldsurface of mold tool (20) for improved processing of first ply laydownas described herein or applied directly to one or both surfaces ofthermoplastic fiber reinforced composite material (60) beforeapplication to the mold tool.

The morphology of the high performance thermoplastic polymer can beamorphous and/or a slow crystallizing (i.e., low crystallinity—typicallyless than 20% crystallinity) semi-crystalline polymer. Blends ofamorphous and semi-crystalline polymers are also contemplated for use asthe surface layer polymer coating (50). In certain embodiments, the highperformance thermoplastic polymer for thermoplastic surface layerpolymer coating (50) is chosen from polyaryletherketones (PAEK),polyetherimide (PEI), polyimides, PAEK co-polymer with PEI and/orpolyethersulfone (PES) and/or polyphenylenesulfide (PPS), and PAEKblends with one or more of PEI, PES, PPS and/or polyimides.

In particular embodiments, for example, thermoplastic surface layerpolymer coating includes PAEK chosen from polyetheretherketone (PEEK) orpolyetherketoneketone (PEKK) and blends with, such as, but not limitedto, diphenylsulfone. When the thermoplastic surface layer polymerincludes PEKK, the T:I ratio of the PEKK ranges from about 0:100 toabout 70:30 in order to maintain the slow crystallization rate of thesurface layer polymer. In a particular embodiment, the T:I ratio of thethermoplastic surface layer polymer uses CYPEK® DS that has a T:I ratioof from about 0:100 to about 70:30. Suitable PEKK polymers available foruse with the present invention include, but are not limited thosecommercially available from Cytec Industries Inc., Woodland Park N.J.,such as CYPEK® DS-E or CYPEK® DS-M and CYPEK® HT.

The surface layer polymer coating (50) can further include one or moremulti-functional agents chosen for improving the resulting thermoplasticcomposite part features, such as electrical conductivity, toughness,oxygen permeability, crystallization rate and/or solvent resistance ofthe resulting thermoplastic composite part. Such multi-functional agentsmay be in the form of a metallic coating and/or micro- and/ornano-particles.

The optional surface layer polymer coating (50) multi-functional agentscan include one or more of materials such as, but not limited to, impactmodifiers, mold release agents, lubricants, thixotropes, antioxidants,UV absorbers, heat stabilizers, flame retardants, pigments, colorants,layered colorants for impact damage indicators, nonfibrousreinforcements and fillers, nano-graphite platelets, to enhancecrystallinity rate and mitigate shrinkage, nano-clays to improve solventresistance, nano-metals (such as nickel fibrils), particle interleavingfor impact toughening, CVD veil fabrics in interleave for OML lightningstrike, fiber or polymer veils to improve impact performance, surfacefinishes to aid in air removal as the pressure is applied by the ATLmachine, and high flow surface coatings to speed reptation healingacross the inter-ply region.

The mold tool (20) can be of any non-porous high temperature toolingincluding metal. Metal tooling, preferably stainless steel, invar or lowcarbon steel as known to one skilled in the art are all appropriate. Themold surface of the mold tool (20) can be stainless steel able towithstand the high processing temperatures required for thermoplasticfiber reinforced composite part manufacturing and low CTE, but ispreferably invar. High temperature tooling is capable of withstandingprocessing temperatures up to 800° F. (427° C.). Mold tool (20) can be a0.120″ thick 304 stainless steel plate or 0.063″ invar 36. However, thestainless steel plate may not be as effective as invar due to higherdifferential CTE, which can cause delamination during processing of thethermoplastic fiber reinforced composite material from the mold surfaceof the mold tool.

The mold tool (20) should be a solid, impermeable material that isnon-porous. The mold tool (20) should not allow the flow of air or gasesthrough its mold surface.

A textured mold surface (30) is preferably created on the mold surfaceof the mold tool (20) in order to improve mechanical adhesion of thesurface layer polymer (50) to the mold tool (20) in an effort toovercome the CTE differential delaminating the thermoplastic fiberreinforced composite material (60) and surface layer polymer coating(50) from the mold surface of mold tool (20). The textured mold surface(30) is believed to provide a mechanical interlock between the mold tool(20) and the surface layer polymer coating (50), as well as improveadhesion in order to overcome differences in coefficient of thermalexpansion between the surface layer polymer coating (50) and the moldtool (20). Too little texture and the mechanical interlock will beinsufficient to overcome the CTE differential, resulting in the surfacelayer polymer coating (50) easily peeling off of the mold tool (20)during manufacture. Too course of textured mold surface (30) can resultin a surface layer polymer coating (50) that can be difficult to releaseand remove without causing damage to the surface layer polymer coating(50) when trying to remove the resulting composite part from the moldtool.

The textured mold surface (30) cab be added by many means such assandblasting, milling, Blanchard grinding, glass bead blasting,knurling, or other means to texture the mold surface to accept therelease film (40). Creation of the textured mold surface (30) can beaccomplished by a method such as sandblasting with a grit size fromabout 20 grit to about 180 grit, and more preferably 40 grit to 120grit. In particular, about 120 grit aluminum oxide or about 40-60 gritglass beads provide an even texture on the surface and are preferredwith the 40-60 grit glass beads being optimal. The preferred methods ofapplying an appropriate texture is by sandblasting with 120 gritaluminum oxide or 40-60 grit glass beads.

The appropriate texture for a particular combination of mold surface ofa mold tool (20) and surface layer polymer coating (50) can be optimizedby one skilled in the art to identify the most appropriate level oftexture for a particular surface layer polymer coating (50) and moldtool (20). One skilled in the art will be able to identify the mostappropriate level of texture for the type of mold tool material andsurface layer polymer coating material to overcome the CTE differencesinvolved to support sufficient adhesion while maintaining releasabilityof the resulting composite part.

One method of quantifying an appropriate level of texture is bymeasuring the profile elements of a textured mold surface (30). Both agreater mean spacing of profile elements and greater depth of profileelements are appropriate methods of distinguishing preferred levels oftexture. Both profile elements need to be appropriate for the texture tobe appropriate.

A high temperature mold tool and a thermoplastic surface layer polymercoating, a 0.063″ invar 36 sheet with a PEKK surface layer polymercoating, was tested with a Time Group Inc. TR200 diamond stylus tipsurface profilometer, inductance type surface roughness tester. Thesurface profilometer uses a diamond stylus that is moved at a controlledspeed over the surface of the sample to detect characteristics of thematerial. These parameters are measured on a flat sample by resting thedevice on top of the sample. This is test is performed at standard roomtemperature and humidity and the mold tool tested should be at roomtemperature. The profilometer is set onto the sample in the x-direction(defined as parallel to the edge of the test bench) and the test isbegun using the play arrow key and all parameters are recorded for theX-direction. The profilometer is then repositioned perpendicular to theprevious test and the test is repeated to record all parameters for theY-direction.

This Rsm calculation is illustrated in Formula 1, with R_(Y) illustratedin Formula 2. As seen in Table 1 below, a combination of maximumpeak-to-peak measurement profile height was found to be the bestcharacteristic of optimal texture. Values greater than those shown inTable 1 may be obtained and used. However, greater values may adverselyincrease mechanical adhesion, impact resulting composite part dimension,and distort tolerances.

TABLE 1 (Micro Invar Meters) 36 120 Tool Stainless 120 40-60 Mill gritfinish Steel grit 40-60 Glass scale AlO₂ Direction Description SmoothAlO₂ glass X X Y X1 X2 X3 Y Rsm mean spacing of profile 0.160 0.1140.093 0.167 0.200 0.182 0.070 0.071 0.068 0.067 elements R_(Y) Maximumheight of 1.391 4.707 7.28 6.255 7.059 6.664 7.288 7.084 7.032 5.947profile

The mold release film (40) can be applied to the mold surface of moldtool (20) after applying textured mold surface (30) to the mold tool toevenly and uniformly cover the mold surface of the mold tool (20). Themold release film (40) further provides the appropriate releasableadhesion of the surface layer polymer coating (50) to the mold surfaceof the mold tool (20). The mold release film (40) may only partiallycover the textured mold surface (30) of the mold tool (20), so long asit covers that recommended by the mold release manufacturer.

The mold release film (40) functions as an interface between thetextured mold surface (30) of the mold tool (20) and the surface layerpolymer coating (50). The mold release film (40) also provides achemical bonding to restrain the surface layer polymer coating (50) onthe mold surface, thereby maintaining optimal adhesion and subsequentreleasability of the surface layer polymer coating to the mold surfaceduring application of the thermoplastic fiber reinforced compositematerial. The mold release film (40) is also robust enough to survivethe intense heat and conditions from the laydown process such that itprovides a release layer to separate the surface layer polymer coating(50) from the mold tool (20) once the resulting composite part has beencured.

Mold release film materials are commercially available and areadvertised as capable of releasing the product from a mold tool afterprocessing. Suitable commercial mold release film include Hysol Frekote800, AXEL 21RM, AXEL 21LS, and AXEL W-4005. The release agent ispreferably high temperature AXEL W-4005 applied and seasoned per themanufacturer's specifications.

The mold tool (20) together with the mold release film (40) can then beheated to “season” as recommended by the supplier.

A sealer can optionally be applied to the mold surface of mold tool (20)as recommended by the mold tool manufacturer prior to application of themold release film (40) to further increase the releasable adhesion ofthe surface layer polymer coating (50) and allow release of theresulting composite part from the mold surface.

Fiber reinforced composite material (60) are structural reinforcementfiber materials, pre-impregnated with an appropriate high performancethermoplastic polymer matrix resin. These are generally categorized astape, woven cloth, non-woven cloth, paper, and mixtures thereof.

Suitable structural reinforcement fibers for fiber reinforcement includeany of the commercially available structural fibers such as carbonfibers, Kevlar® fibers, glass fibers, aramid fibers, and mixturesthereof. In a preferred embodiment the fibrous structural reinforcementfiber is a polyacrylonitrile (PAN) based carbon fiber.

The fibrous structural reinforcement can be configured in aunidirectional tape (uni-tape) web, non-woven mat or veil, fiber tow, orfabric material. Tape prepreg generally refers to unidirectionalstructural reinforcement fibers that extend along a single axis of thestrip material. Tape prepreg is generally used for ATL laydownapplications. The term “cloth” generally refers to structuralreinforcement fibers laid along at least two different axes within thestrip material. Cloth is commercially available as bi-axial, tri-axialand quad-axial, indicating fibers extending in two, three, or fourdifferent axes, respectively. The fibers may optionally be woven withone another, or may be manufactured as non-woven cloth. Cloth prepregmaterials are generally used for hand laydown applications.

Fiber reinforced composite material (60) contains any of the fibrousstructural reinforcement fiber described herein that has beenimpregnated with at least one high performance thermoplastic polymer viaany manufacturing/impregnation method known to those of skill in theart. Suitable impregnation methods are known to those of ordinary skillin the art and include, for example and without limitation, hot-meltimpregnation, aqueous slurry impregnation, powder coating, extrusionfilm lamination, and combinations thereof.

The high performance thermoplastic polymer for the surface layer coating(50) and the high performance thermoplastic polymer as the matrix resinfor the fiber reinforced thermoplastic composite material (60) can bethe same or different materials or combinations thereof.

The term “high performance polymer” is meant to refer to anythermoplastic polymer that has a melting temperature (Tm) greater thanor equal to 280° C. and a process temperature (Tprocess) greater than orequal to 310° C. In certain embodiments, the higher performance polymeris chosen from polyaryletherketones (PAEK), PAEK blends, polyimides, andpolyphenylenesulfides (PPS).

In certain embodiments, the PAEK is chosen from polyetheretherketone(PEEK), polyetheretherketoneketone (PEEKK), polyetherketoneketone(PEKK), polyetherketone (PEK), and polyetherketoneketoneetherketone(PEKKEK). In still other embodiments, the high performance polymer is aPAEK blend having polyetherimide, polyphenylene sulfide and/orpolyethersulfone mixed in with one or more polyaryletherketones.

Polyaryletherketones are well known to those skilled in the compositearts and include, but are not limited to, APC-2® PEEK, CYPEK®-FC and/orCYPEK®-HT, all commercially available from Cytec Industries Inc.,Woodland Park, N.J.

Resin content of the high performance thermoplastic polymer resin in thefiber reinforced composite material (60) ranges from about 26% to about90% by weight of the total thereby providing composite material (60)with a resin modulus of 500 ksi or greater and an interlaminar fracturetoughness of 600 J/m² or greater as measure by G_(1c). The viscosity ofthe high performance polymer is adjusted so that good filament wet outis obtained. Ultimately, the high performance polymer of the fiberreinforced composite material acts as part of a polymer matrix and formsa polymer blend with the surface layer polymer coating (50) when thematerials are contacted. As used herein, the term “polymer blend”includes miscible and compatible polymer blends as those terms are knownand understood by those skilled in the art to which the inventionpertains.

The resulting thermoplastic composite parts formed by the presentinvention can be various articles formed using rapid lamination andforming processes including, but not limited to, in situ thermoplastictape/tow placement for stiffened wing and fuselage skins, continuouscompression molding (CCM) and roll forming process for stiffenerfabrication, double belt press to make consolidated flat panels andaircraft floor panels, in situ filament wound cylindrical structures,and fusion bonding and welding of composite assembly.

The following examples are provided to assist one skilled in the art tofurther understand certain embodiments of the present invention. Theseexamples are intended for illustration purposes and are not to beconstrued as limiting the scope of the various embodiments of thepresent invention.

Example 1 Solvent Based PEI Polymer Sprayed Solution Applied to Tool

A formulation of PEI polymer, GE Ultem 1000P at 10% plus Dioxilane at90% was plasma sprayed onto the mold surface of a steel mold tool whichhad a release film using an HVLP applicator.

To test the transfer of the PEI/Dioxilane first ply lay-down fiberreinforced thermoplastic composite, an 8 ply quasi-isotropic panel wascreated using APC PEKK/AS-4 uni-tape material. The panel was processedwith a caul plate at an autoclave temperature of 720° F. (382° C.) and100 psi of N₂. The panel showed some surface anomalies on the coatedface.

Example 2 Water Based Slurry Hand Applied to Tool

A direct hand application technique was attempted using a mixture thatincluded surfactant, water, hydrosize (sizing) and thermoplastic, asfollows: 1) Sizing 90%/PEKK 10%. 2) D.I water 80%/Surfactant10%/PEI-Diox. Premix solution 10%. 3) D.I water 80%/Surfactant 10%/PEKK10%. 4) Sizing 80%/PEI powder 10%/Surfactant 10%). The resulting waterbased slurry thermoplastic surface layer polymer coating shrank rapidlyon the mold surface of the mold tool and did not achieve adequatebonding onto metal mold tool. The surface layer polymer coating flakedoff very easily with minimum abrasion.

Example 3 PEK Polymer Plasma Sprayed onto Mold Tool

To impart a coating directly onto the mold surface of a mold toolapplied with a sealer and release film, a plasma spray coating wasperformed using a Praxair SG 100 plasma gun and introduced PEK polymerinto the jet stream to heat and accelerate the material to highvelocity. Initially there was difficulty maintaining adhesion betweenthe sealed/released tool and the PEK polymer, when the tool was allowedto cool to room temperature, likely caused by the difference in CTE(coefficient of thermal expansion) of the mold tool and thethermoplastic surface layer polymer coating on the smooth mold surfaceof the mold tool. It appeared that the skin coating released from thetool (Hysol® Frekote® GP sealer agent and release agent Frekote® 800).

Example 4 PEK Polymer Plasma Sprayed onto Textured Mold Surface of MoldTool

To improve adhesion of the plasma PEK polymer spray, a subsequent panelwas sandblasted using 120 grit aluminum oxide and release coated withFrekote® 800. A much better coating application was achieved.

To test how the PEK plasma-sprayed coatings transferred to a laminate,two 8-ply quasi-isotropic panels were created using APC PEKK/AS-4uni-tape material. The panels were processed with a caul plate at anautoclave temperature of 720° F. (382° C.) and 100 psi of N₂.

The resulting panels showed some uneven surface texture and surfacelayer polymer coating thickness. Some areas of the surface coating couldbe scraped off the resulting thermoplastic fiber reinforced compositepart. The mold surface of the mold tool was clean after the autoclavecycle, indicating the mold release was effective.

Example 5 Plasma PEK Polymer Sprayed Coating onto Prepreg

Plasma spraying was also conducted on APC-uni-tape samples to provide apath to adding material to the outside of a thermoplastic material. Twocoated weights were deposited to test the process control. Only one sideof the tape was coated. Transverse resin shrinkage and wrinkling of thetape was noted.

The unique capabilities of this process offer beneficial uses such ascombinations of materials including ceramic, metallic and polymer blendsthat would be difficult to produce by other means. Metal alloy coatingsmay provide improved electrical conductivity for lightning strike andedge glow reduction.

Example 6

Thermoplastic composite parts are processed at high temperatures andrequire stable tooling materials. The processing cycle for PEKK-FCuni-tape panels exceeds 730° F. (388° C.) which necessitates steel alloytooling. For this series of experiments the tooling was 0.120″ thick 304stainless steel plate.

Multiple surface finishes were tried during this experiment. The defaultsmooth panel was a 0.125″ thick stainless steel plate that had beensanded with 120 grit sandpaper and solvent cleaned. The textured surfacetreatments used included 120 grit aluminum oxide and 40-60 c grit glassbead blasting. These surfaces increased the mechanical locking of thefirst-ply coating to the release-coated material. It is believed thatthe surface also broke up the resin film by creating thick and thinareas that reduce the effect of the resin shrinkage on tool adhesion.The glass-bead blasted tool is recommended for plasma spraying but hadnot yet been tried. The benefit of the texture is that it aids retentionof the coating during processing.

Zyvax Sealer GP was initially used to seal the stainless plates. Thiswas found to interact with the Frekote® 800 to produce a surface with anexceptionally easy release. This causes premature slip of the coating onthe tool. After this was discovered, the sealer was mechanically removedfrom all surfaces and discontinued.

The first mold release evaluated was Hysol® Frekote® 800. Thissolvent-based system is known to offer release at processingtemperatures above 400° C. The release was wiped onto the stainlesssteel surface and allowed to air dry, and then the tools were plasmasprayed with thermoplastic. Initial coating used the PEI/dioxilane sprayand showed a tendency to peel off the tool with minimal abrasion.Kant-Stik Cure-Fast mold release was then tried and was also found tohave an easy-release surface. This release has proven difficult toprocess above 750° F. (399° C.).

AXEL 21RM mold release was then used without a sealer and appeared tohave a “tighter” surface than any of the previous releases. It is asolvent-based system. The Axel 21RM is the preferred available releasefor this application. It works without a sealer to provide good surfaceadhesion without being too slippery. A water-based version, W4005, wasalso tried to compare to the AXEL 21RM, but found to be sensitive toabrasion with small “marbles” of release evident after some fingerabrasion of the tool.

In keeping with the release manufacturer's recommendations, the toolswere heated to the use temperature (735° F., 391° C.) to season therelease onto the tool. Seasoning the tool allows the release to be curedonto the tool before entering service. This step was included to preventsolvent from the first ply laydown using the PEI/dioxilane solution fromlifting the mold release film.

Example 7

To impart a coating directly onto a release-coated tool, a plasma spraycoating was performed using a plasma gun and introduced PEK polymer intothe jet stream to heat and accelerate the material to high velocity. ThePEK polymer is fed to the plasma gun using a fluidized bed feedersystem.

This time the tool was pre-heated to 250° F. (121° C.) to aid inadhering the polymer to the surface of the tool. A Praxair SG 100 plasmagun was used to deposit approximately 2 mils of PEK polymer on to thetool. This temporarily deposits the powder onto the tool. The stainlesssteel tools with the powder coating were then processed in an electricfurnace at 750° F. (399° C.) to melt the polymer and create a meltedpolymer layer.

To improve adhesion of the plasma spray, a subsequent panel wassandblasted using 120 grit aluminum oxide and release coated with Hysol®Frekote® 800. A picture frame of tape was placed on the tool to create arough center panel and a smooth perimeter. This picture frame wasintended to show the effect of surface roughness transitions on thefirst ply lay-down materials. This also provides a smooth area formasking off tool overspray.

To test how the PEK plasma-sprayed coatings transferred to a laminate,an 8-ply quasiisotropic panel was created using APC PEKK/AS-4 uni-tapematerial. The panel was processed with a caul plate at an autoclavetemperature of 720° F. (382° C.) and 100 psi of N₂. The resulting panelshowed somewhat un-even texture and coating thickness. The coated toolsurfaces were clean after the autoclave cycle, indicating the moldrelease was effective.

Film Lamination using bi- or tri-layer in situ thermoplastic tape: Asmall press was heated to between 290° C. and 410° C. Kapton film iscoated with a release agent and, with the press at the desiredtemperature; a bi- or tri-layer configuration is sandwiched between twopieces of the release agent coated Kapton film, thereby forming alay-up. The lay-up is placed between the two 3″×3″ stainless steel caulplates of the press along with a thermocouple. The stack is insertedinto the press and 1,000 pounds of pressure is applied and held for aperiod of from 10 to 30 seconds. The pressure and top plate is thenreleased and the stack is removed to cool under a cold press (1000 lbs.for 1 minute).

In view of the above description and examples, one of ordinary skill inthe art will be able to practice the disclosure as claimed without undueexperimentation.

Although the foregoing description has shown, described, and pointed outthe fundamental novel features of the present teachings, it will beunderstood that various omissions, substitutions, and changes in theform of the detail of the apparatus as illustrated, as well as the usesthereof, may be made by those skilled in the art, without departing fromthe scope of the present teachings. Consequently, the scope of thepresent teachings should not be limited to the foregoing discussion, butshould be defined by the appended claims.

We claim:
 1. A tool for automated tape laying of in situ thermoplasticfiber reinforced composite materials comprising: a non-porous solidmetal mold tool having a molding surface; and a thermoplastic surfacelayer polymer; and a release film releasably interposed between the moldsurface of the mold tool and the thermoplastic surface layer polymer. 2.The tool according to claim 1, wherein the mold surface of the mold toolhas a texture.
 3. The tool according to claim 2, wherein the texture ofthe mold surface of the mold tool is created by sandblasting with 40-120grit glass beads.
 4. The tool according to claim 2, wherein the textureof the mold surface of the mold tool has a mean spacing of profileelements of 0.07 μm or greater and a maximum height of profile of 5.0 orgreater.
 5. The tool according to claim 1, wherein the thermoplasticsurface layer polymer is chosen from PEK, PEKK, PEEK or blends thereof.6. The tool according to claim 1, wherein the thermoplastic surfacelayer polymer further comprises one or more multi-functional agents. 7.The tool according to claim 1, wherein the thermoplastic surface layerpolymer is a discontinuous plurality of well fused thermoplasticparticles releasably adhered to the release film.
 8. The tool accordingto claim 1, wherein the thermoplastic surface layer polymer is appliedby plasma spray.
 9. The tool according to claim 1, wherein thenon-porous metal mold tool having a mold surface further has texture;wherein the release film adheres to the mold surface of the mold tool;and wherein the thermoplastic surface layer polymer coating comprises aplurality of thermoplastic surface layer polymer particles applied byplasma spraying; wherein the thermoplastic surface layer polymer coatingis a discontinuous plurality of beads that are well fused thermoplasticparticles releasably adhered to the release film.
 10. The tool accordingto claim 9 wherein the texture of the mold surface of the mold tool hasa mean spacing of profile elements 0.07 μm or greater and a maximumheight of profile about 5.0 or greater.
 11. The tool according to claim9 wherein the thermoplastic surface layer polymer particle has adiameter D₉₀ size of 90 to 180 μm before plasma spraying.
 12. A prepregfor automated tape laying of in situ thermoplastic fiber reinforcedcomposite materials comprising: a thermoplastic fiber reinforcedcomposite material having a first surface and a second surface; and athermoplastic surface layer polymer on at least the first surface. 13.The prepreg according to claim 12, wherein the prepreg comprises athermoplastic surface layer polymer on the first surface and the secondsurface.
 14. A method for preparing a mold tool able to accept a firstply laydown of thermoplastic fiber reinforced composite material forautomated tape laying of in situ thermoplastic composite materialscomprising: providing a non-porous metal mold tool having a moldsurface; applying a texture to the mold surface of the mold tool;applying a release film to the texture on the mold surface of the moldtool; introducing a plurality of thermoplastic surface layer polymerparticles to a plasma spray gun; and plasma spraying the thermoplasticsurface layer polymer particles onto the release film on the mold toolduring in situ tape laydown of a thermoplastic fiber reinforcedcomposite material.
 15. The method for preparing a mold tool accordingto claim 14 wherein the thermoplastic surface layer polymer particlesintroduced to the plasma spray gun is PEKK particles having a diameterD₉₀ size of 90-180 μm before plasma spraying.
 16. The method forpreparing a mold tool according to claim 14 further comprising applyingheat to the molding tool after application of the thermoplastic surfacelayer polymer to anneal or crystallize the thermoplastic surface layerpolymer.
 17. A method of automated tape laying of in situ thermoplasticfiber reinforced composite material comprising: providing a non-porousmold tool having a mold surface; applying a release film to the moldsurface of the mold tool; introducing a plurality of thermoplasticsurface layer polymer particles to a plasma spray gun; plasma sprayingthe thermoplastic surface layer polymer particles on the release film toform a thermoplastic surface layer polymer coating on the mold toolduring in situ tape laydown of a first layer of thermoplastic fiberreinforced composite material having a first surface in contact with thethermoplastic surface layer polymer coating and a second surface; plasmaspraying the thermoplastic surface layer polymer particles on the secondsurface of the first layer of thermoplastic fiber reinforced compositematerials during the in-situ tape laydown of a subsequent layer ofthermoplastic fiber reinforced composite material having a first surfaceand a second surface to form a thermoplastic polymer interlaminar layerbetween the second surface of the first layer of thermoplastic fiberreinforced composite material and the first surface of the subsequentlayer of thermoplastic fiber reinforced composite material; andcontinued plasma spraying of thermoplastic surface layer polymerparticles on the subsequent layer of thermoplastic fiber reinforcedcomposite materials during the in situ tape laydown until desired numberof layers of thermoplastic fiber reinforced composite material areapplied to form a thermoplastic polymer interlaminar layer between eachlayer of thermoplastic fiber reinforced composite material.
 18. Athermoplastic fiber reinforced composite part created using a mold toolaccording to claim 1, wherein the resulting thermoplastic fiberreinforced composite part has enhanced surface properties.
 19. Thethermoplastic fiber reinforced composite part of claim 18 wherein theenhanced surface property is electrical conductivity.